1. Field of the Invention
The present invention relates to a novel target for identifying and/or screening antitumor and/or antiangiogenesis agents using the rcl encoded deoxynucleoside 5′monophosphate N-glycosidase.
2. Description of the Related Art
The c-Myc transcription factor plays an important role in the regulation of the cell cycle, cellular transformation and apoptosis (Eisenman, R. N. (2001) Genes Dev 15, 2023-30) as well as in the genesis of many human cancers (Nesbit, et al (1999) Oncogene 18, 3004-16). The deregulation of MYC expression by chromosomal translocation, amplification or altered signal transduction is commonly found in human cancers (Escot, et al (1986) Proc Natl Acad Sci USA 83, 4834-8; Little, et al (1983) Nature 306, 194-6.). In order to elucidate the mechanisms by which c-Myc contributes to tumorigenesis, several approaches have been used to identify its target genes that are compiled in a database (http://www.myccancergene.org/site/mycTargetDB.asp).
Rcl was identified as a c-Myc target by representational difference analysis between non-adherent Rat1a fibroblasts and Rat 1a cells transformed by MYC (Lewis, et al (1997) Mol Cell Biol 17, 4967-78). Rcl is expressed at a low level in untransformed cell lines while it is significantly elevated in breast cancer and lymphoma cell lines (Lewis, et al (1997) Mol Cell Biol 17, 4967-78). Moreover, Rcl is one of the most responsive target to Myc activation in vitro and in Myc-induced transgenic lymphoma (Kim, et al (2003) Mol Cell 11, 1177-88; Keller, et al (2005) Oncogene 24, 6231-40), and Rcl has been shown to be a direct Myc target in a human lymphoma cell model (Zeller, et al. (2003) Genome Biol 4, R69). Serial analysis of gene expression studies revealed that Rcl is also highly expressed in human glioblastoma multiforme as compared with normal human brain (information from the UniGene database, at NCBI). Furthermore, Rcl is among the top 50 genes whose overexpression distinguishes between benign and malignant prostate tissues (Rhodes, et al (2002) Cancer Res 62, 4427-33). Functionally, Rcl has transforming activity in Rat1a cells when coexpressed with either vascular endothelial growth factor (VEGF) or lactate dehydrogenase (LDHA) (Lewis, et al (2000) Cancer Res 60, 6178-83). Altogether these data suggest that RCL could be a prime therapeutic target.
RCL appears to be a nuclear 22 kDa protein with yet unknown function. The closest relative of RCL protein is the nucleoside 2-deoxyribosyltransferase family (EC: 2.4.2.6). (pfam 05014) that catalyzes the reversible transfer of the deoxyribosyl moiety from a deoxynucleoside donor to an acceptor nucleobase (Macnutt, W. S. (1952) Biochem J 50, 384-97; Uerkvitz, W. (1971) Eur J Biochem 23, 387-95; Holguin-Hueso, J. & Cardinaud, R. (1972) FEBS Lett 20, 171-173). Here, we report the purification and characterization of the recombinant RCL from rat. RCL is a deoxynucleoside 5′-monophosphate N-glycosidase, a function never described before.